1. Field of the Invention
Example embodiments relate to a method and apparatus for calibrating a difference by transmission path in a wireless communication system which employs beamforming using an antenna array.
2. Description of the Related Art
In recent years, there is a dramatically growing demand for services which transmit and receive massive data, such as video and audio data, at high speed. Accordingly, studies are actively being conducted on use or spatial splitting of a high-frequency band, such as millimeter waves, to increase a transmission rate.
Beamforming using an antenna array is employed as a representative method in order to spatially collect wave signals.
A basic principle of beamforming is collecting signals in a desired direction to increase gain and offsetting signals in an undesired direction to reduce gain
Use of beamforming increases transmission distance or reduces output power, thus enabling low-power operations and providing a spatial filter function which reduces surrounding interference signals.
As beamforming uses a plurality of antennas and radio frequency (RF) transceivers, it is necessary to calibrate differences between different antennas and between different RF transceivers in order to maintain stable performance.
Also, in a general beamforming technique, a reception path can be calibrated using a signal directly received by an antenna and thus is managed by a comparatively large number of methods. However, a transmission path does not directly receive a signal radiated by an antenna, making it difficult to calibrate a transmission signal.
Generally, beamforming has a complicate structure, which needs a reference signal for transmission path calibration and a receiver for receiving a signal, and has difficulty in performing continuous calibration during communications.